1. Write Linear Equations
Chapter 9 Lesson 2
Write Linear Equations
Pg. 685

2. What we Know so far…. Direct Variation Where k is the slope and
Slope Intercept Form
Where k is the slope and
“0” (origin) is the y-intercept
Where m is the slope and
b is the y-intercept
In order to graph a line,
we need the slope and a point

3. Where two points are given as (x1,y1) and (x2,y2)
What we Know so far….
Slope
Where two points are given as (x1,y1) and (x2,y2)

4. The Old Stuff… Writing equations
Slope-intercept form is:
Where m is the slope and
b is the y-intercept
Example: Find the equation of the line with
“m” = slope = -2 and “b” = y-intercept = 8
y = -2x + 8
Easy if I know the y-intercept… but if I don’t?

5. The New Stuff… Point - Slope Form
Point - Slope form is:
Where m is the slope and
(x1,y1) is the given point that the line goes through

6. The New Stuff… Point- Slope Form
Point- Slope form is:
Where does this equation come from?
The Slope Formula

7. The New Stuff… Point- Slope Form
Point- Slope form is:
Attached to the “x” is the “x-coordinate”
Attached to the “y” is the “y-coordinate”
m = 5 , (4, 7)
m = -2 , (4, - 7)

8. m = -5, (-3, 2)
m = , (8, -4)

9. If you are given the equation in
Remember….
If you are given the equation in
Point-Slope Form,
and you are asked to graph, the (x1, y1) are opposite from how they appear.

10. Using Point-Slope Form to graph1 2 4 3 5 -1 -2 -3 -4 -5
Slope is
Point is (2,3)

11. Change Point-Slope Form to Slope-Intercept form

12. Change Point-Slope Form to Slope-Intercept form

13. Your turn
m = (1, 1)

14. Your turn
m = ( -3, 4)

15. What do we do if they give 2 Points (-3, 6) and (1, -2)?

16. Homework Pg
RC: 1 – 11, 14
HC: 1 – 14